In the compelling need for decarbonization of the transport and energy sectors, hydrogen could play an important role, both as an energy carrier and as a long-term storage medium for intermittent renewable energies such as solar and wind. The usage of hydrogen as a fuel for the transport sector seems to be the optimal solution wherever weight and range are the main constraints, like for heavy-duty transport, trains, cargo ships, and airplanes. Hydrogen chemical energy can be converted into mechanical or electrical energy mainly in two ways, by means of a combustion process in Internal Combustion Engines, or by means of electrochemical conversion in Fuel Cells.